Author:

The resistive wall mode (RWM) is a macroscopic instability that can severely
limit the achievable plasma pressure, and hence the eventual fusion power
production, in present and future tokamak devices. Therefore, understanding
the physics associated with this instability, and learning how to control
it, is of critical importance in future devices such as ITER, in particular
in the so called advanced tokamak scenarios. During recent years, it has
been realized that kinetic effects, due to the mode resonance with drift
motions of both thermal and energetic particles (EPs), can play a crucial
role in stabilizing/destabilizing the RWM. The mode physics in such cases
are well described by the MHD-kinetic hybrid approach.
This contribution reports the recent new developments in the RWM theory,
based on a non-perturbative, or self-consistent, approach for numerical
modelling of the RWM stability in the presence of energetic particles. Two
important aspects of the EPs effects are examined: (i) the anisotropy of the
equilibrium distribution in the phase space, in particular along the
particle pitch angle; and (ii) the finite orbit width (FOW) effect of EPs on
the mode stability. Both effects have been studied within the so called
perturbative approach. In particular, it has been found from a recent study,
Ref. [1] below, that for the target plasma as envisaged in the ITER 9MA
scenario, the RWM is fully stabilized by the kinetic effects from thermal
and energetic particles. The FOW of EPs plays an essential role in the mode
damping. Given the fact that the perturbative approach often overestimates
the kinetic damping, as compared to the non-perturbative approach (see e.g.
Ref. [2] below), it is of great interest to understand how the FOW affects
the mode stability following a non-perturbative formulation. Such
formulations have recently been developed, incorporated into the MARS-K
code, and will be presented in this talk. Simulation results will be
reported for full toroidal plasmas such as those designed for the ITER 9MA
steady state scenarios.
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[1] I.T. Chapman, et al., Phys. Plasmas 19, 052502 (2012).\\[0pt]
[2] Y.Q. Liu, Nucl. Fusion 50, 095008 (2010)

*Work performed in collaboration with CRPP, SWIP, GA, PPPL, and carried out within the framework of the European Fusion Development Agreement, partly funded by EURATOM, UK EPSRC, and the US Department of Energy.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2013.DPP.BI2.6